Various packing boxes for transporting and storing a reagent container containing a reagent to use for an analyzer, and the like have been proposed. A reagent container filled with reagent and an empty drainage container containing drainage from the analyzer are accommodated in a packing box as a set (see for example U.S. Pat. No. 8,679,425).
In the technology described in U.S. Pat. No. 8,679,425, the reagent container filled with reagent and the drainage container inflated by sealing gas are inserted into a box main body, and thereafter, a container holding member is arranged in the box main body, and a flange-shaped lock portion on a lower side of a mouth portion of each container is locked to a circumferential edge of a holding hole formed at an upper surface part of the container holding member. In this case, the mouth portion of the container needs to be pulled out from the holding hole using fingers, which is a troublesome task. The mouth portion can be easily pulled out by enlarging the holding hole, but in this case, a gap between the holding hole and the mouth portion becomes too large and the container cannot be stably positioned.